As the density of integrated circuit chips increase and the physical image sizes decrease, defect inspection of the photomasks used to fabricate integrated circuit chips has become ever more important. These images have become far too small and numerous for human visual inspection and verification. Therefore machine inspection methods have developed. However, there are regions on photomasks that are printed on wafers during manufacture of integrated circuit chips that repeat and other regions that do not repeat. Inspection of repeating images and of non-repeating images require different machine methods of inspection. Implementing two machine methods in a mask manufacturing facility can be expensive and time consuming.
Therefore, there is a need for a single machine methodology for inspecting photomasks having regions that repeat and regions that do not repeat.